The present invention relates to multi-line wireless telephone systems and, in particular, to techniques for conserving power in battery-operated wireless handsets in wireless telephone systems.
The use of telephones and telephone systems, including wireless telephone systems, is widespread. In wireless telephone systems, a cordless or wireless telephone handset unit communicates via either analog or digital radio signals with a base unit, which is typically connected via a standard telephone line to an external telephone network. In this manner, a user may employ the wireless handset to engage in a telephone call with another user through the base unit and the telephone network.
Multi-line wireless telephone systems are also in use in various situations, such as businesses with many telephone users. Such systems employ a handset that communicates with up to N handsets simultaneously, typically with digital communications schemes, such as a spread-spectrum, time division multiple access (TDMA). In a TDMA system, a single RF channel is used, and each handset transmits and receives data during a dedicated time slice or slot within an overall cycle or epoch. During other time slots of the epoch, the handset is in an xe2x80x9coffxe2x80x9d state to conserve power.
In such systems, the handsets are typically battery-powered. Efficient power use is therefore important for a wireless system, in part to conserve handset battery power. In addition, too much power used to transmit signals from a handset can cause communication problems such as saturation of the receivers.
Thus, various techniques are typically employed to conserve power in wireless handsets, such as handsets of a digital wireless telephone system. For example, in one technique, the handset is put in a sleep mode where all but a watchdog function are powered down. However, in such a system, the handset may be moved from the position when it last communicated with the base unit. This can cause the handset to utilize too much power when communication needs to be reestablished. This excessive initial power use can saturate the base unit receiver, delay synchronization, and drain unnecessary power from the handset battery.
A wireless telephone system having a plurality of wireless, battery-powered handsets and a base unit, the base unit having a base transceiver. Each handset has a handset transceiver for establishing a wireless link over a shared channel with the base unit via the base transceiver, wherein the base transceiver transmits to a given handset transceiver a forward data message, which contains forward power level information identifying a forward power level at which the forward data message was transmitted by the base transceiver. The receiver receives and locks onto the forward data message. The transmitter transmits to the base transceiver a return data message at a return power level determined in accordance with the forward power level information.